Introduction: Life changed enormously in the 20th century as air conditioning and refrigeration systems became more efficient and controllable. Air conditioning and refrigeration play an important role in human comfort, food processing, storage and many other industrial processes. We chose this topic because our life would be difficult without air conditioning and refrigeration. This article will talk about the history of air conditioning and refrigeration, the role of engineers in their design and construction, the lives of people before and after air conditioning and refrigeration, and finally the applications in the field of achievements and future developments. The History of Air Conditioning and Refrigeration: Before the 20th century, most efforts were ineffective and people tried many things to provide the comfort of coolness, until Leonard de Vince designed a mechanical fan and whether it is used in industrial environments. Then an engineer named Stuart Cramer, he liked the idea of ​​the latest heat and humidity control system and he improved it and called it "air conditioning" in 1906. A year later, an equipment air conditioning system designed by Witten Meier was installed. in cinemas and hotels. And in 1927, General Electric introduced the first mass-produced refrigerator with a completely sealed refrigeration system and it was one of a kind. In 1927, these improvements continued to advance and engineers completed their research and developed air conditioning and refrigeration to use less energy. Role of Engineers: The main job of engineers is to solve problems and design things that make people's lives easier. One of the problems that refrigeration engineers faced in the early 20th century was how to ...... middle of paper ......r change the phase from gas to liquid. This will allow heat to escape from the condenser. Additionally, the condenser takes care of rejecting heat from the system and does not change the pressure, so the pressure will remain high. • Third, the liquid will enter the regulator with the highest pressure and exit with the lowest pressure. pressure.• Finally, the liquid moves to the evaporator, where heat from the interior air is absorbed and changes it from a liquid to a gas. After that, it returns to the compressor, where the entire cycle is repeated. Compressors used in refrigerators use titanium turbines. Using titanium requires a high level of energy, which makes the cost higher. One of the future technologies that will save energy and reduce costs is the refrigerant known as “R-718” or “Water Vapor”. R718 may be more efficient than our current refrigerants.